Operation of by-product coke oven batteries in the banked state or under &#34;slow-down&#34;conditions



F. WE OPERATION OF BY-PRODUCT COKE OVEN BATTERIES IN T1 1 BANKED STATE OR UNDER "SLOW-DOWN" CONDITIONS Filed Sept. 6, 1960 4 Sheets-Sheet 1 May 19, 1964 THLY 33,869

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REVERSIBLE THERMAL EXPANSION 0F .S/L/CA BRICK EXPANSION PERCENT 1' i n 6. in n a /00 200 500 400 500 6'00 7w 300 9m mm //m I200 am #00 I500 an 1700 mm TEMPERATURE F nae IN V EN TOR. FRI/VS W 717A Y May 19, 1964 F WETHLY 3,133,869

OPERATION OF BY-PRODOCT COKE OVEN BATTERIES IN THE BANKED STATE OR UNDER "SLOW-DOWN" CONDITIONS Filed Sept. 6, 1960 4 Sheets-Sheet 2 INVENTOR. Fii/VS WET/92 E lrrae/wzr 3,133,869 THE F. WETHLY ODU May 19, 1964 OPERATION OF BY-PR CT COKE OVEN BATTERIES IN BANKED STATE 0R UNDER "SLOW-DOWN" CONDITIONS Filed Sept. 6, 1960 4 Sheets-Sheet 3 May 19, 1964 wETHLY I 3,133,869

OPERATION OF BY-PRODUCT COKE OVEN BATTERIES IN THE BANKED STATE OR UNDER "SLOW-DOWN" CONDITIONS Filed Sept. 6, 1960 4 Sheets-Sheet 4 FIG. 5

INVENTOR. Feifis W5 7' 15" Y United States Patent assignor to Allied New York, N.Y., a corporation This invention relates to regenerative coke oven batteries and more particularly to the operation thereof while in the banked state or under slow-down conditions. Because of market conditions for steel, or due to strikes, or for other reasons, it becomes necessary at times to bank a coke oven battery or operate it at a reduced rate. By banked is meant the complete interruption of the operation of the coke oven battery to coke coal in the coking chambers; by slow-down is meant operation of the battery at a reduced rate, say to push coke about once a week as compared with the present common pushing cycle at intervals of to hours duration, usually 16 to 18 hours duration.

Heretofore when the battery was banked, fuel gas was introduced into the base of the heating lines and burned, employing air fed thereto from the inflow regenerators; the products of combustion pass from the flues through the outflow regenerators to the Waste heat duct or ducts communicating with the stack. Periodically, usually about every minutes, the operation is reversed, those dues and regenerators which previously had functioned for inflow, upon reversal function for outflow and those which had functioned for outflow, upon reversal, function for inflow. Of necessity, the amount of gas thus burned in the lines must be appreciably less than that burned during normal conditions of operation when the coking chamber contains the charge of coal to be coked. If the same amount of gas were burned in the flues with the coking chambers empty as when the coking chambers are full, the battery would be heated to such a high temperature that the oven brick-work would be fluxed, and the buckstays, steel work and oven doors would be damaged.

Under slow-down conditions of operation, the amount of gas fed to the fines is materially less than that normally employed, in order to obtain the desired prolongation of the coking cycle. As heretofore practiced, slowdown conditions of operation involve a coking cycle approximately ten or more times as long as the normal cycle when the coking chambers are operated at or near maximum coking capacity.

Hence, during the banked state or under slow-down conditions, the volume of products of combustion passing through the outflow regenerators is markedly less than that which flows therethrough during normal operation. While a relatively small temperature drop takes place in the fines because enough gas is burned in the flues to accomplish this end, a much greater temperature drop occurs in the regenerators due to the greatly reduced volume of combustion products passing therethrough. Cooling of the silica brick regenerator walls and of the regenerator superstructure, which is also of silica brick, thus takes place causing contraction of the silica brick to occur. This contraction may be as much as five or six inches in the length of the walls of the oven chambers and regenerators of a battery, the walls of which are about 40 feet long and even greater in modern coke oven batteries having oven walls approximately 45 or more feet long (the crosswise dimension of the battery).

Contraction of this magnitude has the obvious disadvantages and objections that it results in cracks and fissures in the regenerator walls and in the brick-Work above the regenerator walls between the tops of the regenerators and the bases of the fiues, which brick-work is herein referred to as the regenerator superstructure. Such cracks and fissures not only reduce the effective life of the oven battery, but have the serious disadvantage, particularly in the case or" regenerative coke oyen batteries in which lean gas is burned in the lines and is preheated by flow through the regenerators; that cracks in the regenerators from the outflow waste gas regenerators results in flow of the lean gas through these cracks into the outflow waste gas regenerators. Such leakage of lean gas is promoted by the difierential in pressures between the outflow waste gas regenerators and the inflow lean gas regenerators. The loss of lean gas may be so great as to render uneconomical operation of a battery in which such cracking of the separating walls has taken place.

Were the operation of the batter to be completely interrupted, i.e., no gas be burned in the fiues during the period when economic conditions prevent operation at the usual coking cycle, the temperature drop in the heating walls and regenerators would be so great as to cause contraction of the silica brick-work of which the heating walls and dividing walls of the regenerators are composed of such magnitude as to cause formation of cracks and fissures in the heating walls and regenerator walls with consequent serious damage to the battery, probably to the point where it is more economical to reconstruct the battery than to repair it.

It is a principal object of the present invention to minimize, if not completely prevent such cracking and fissures from taking place in regenerative coking oven batteries during operation thereof in the banked state or under slow-down conditions of operation.

Another object of this invention is to provide a method for operating a coke oven battery under slow-down conditions or in the banked state so that the temperature conditions within the regenerators as well as in the silica brick-work above the regenerators are maintained at all times within a range of such magnitude that little or no contraction or expansion takes place once the battery is heated up to operating temperature and hence the formation of cracks and fissures in the regenerator walls and regenerator superstructure is minimized, if not completely prevented.

Still another object of this invention is to provide a method of operating a coke oven battery in the banked state or under slow-down conditions, which method results in the regenerators being maintained within a temperature range which is substantially the same (or not so greatly different as to cause an excessive reduction in temperature in the regenerators), during each cycle of operation of the regenerators for inflow and outflow, respectively, both during normal operation and during operation in the banked state or under slow-down conditions, thus greatly minimizing, if not completely eliminating the formation of cracks and fissures which would take place in the regenerator walls if the battery were 3 operated first under normal conditions of operation for which the battery is designed and thereafter in the banked state or under slow-down conditions, as heretofore operated.

Other objects and advantages of this invention will be apparent from the following detailed description thereof.

In accordance with this invention, a regenerative coke oven battery is provided with fluid fuel inlets, desirably located at the top of the regenerators, and a fluid fuel such as fuel gas, preferably coke oven gas, if available, or natural gas, i.e., a relatively high B.t.u. gas is supplied to these burners in the outflow regenerators. The fluid fuel thus supplied to the outflow regenerators is burned therein during the outflow cycle of operation of the regenerators. The excess air supplied to the flues to support combustion, which excess air is thus present in the waste heat gases or products of combustion passing through the outflow regenerators provides the necessary oxygen for supporting combustion of the fluid fuel thus introduced into the outflow regenerators. The hot products of combustion thus formed augment the hot gases from the outflow flues and the resultant mixture of gases pass throuhg the outflow regenerators into the waste heat duct. The amount of fuel gas thus burned is controlled to reheat the outflow regenerators to substantially the same temperature as that to which these regenerators are reheated when operated under normal conditions to coke the charge of coal in the coking chambers, or to a temperature such that excessive cooling of the regenerator division walls does not take place. Upon reversal, the fluid fuel is introduced into those regenerators which then become the outflow regenerators and the flow of such fluid fuel to those regenerators which were previously the outflow regenerators and, upon reversal, become the inflow regenerators, is interrupted.

Thus the temperature conditions within the regenerators of the battery when operated under slow-down conditions, or in a banked state, is the same or not sufliciently different to cause excessive cooling of the regenerator walls from taking place as when operated under normal conditions of operation. Hence, stresses and forces due to the temperature drop which takes place due to the greatly reduced flow of products of combustion through the outflow regenerators, which occurs under heretofore known conditions of operation of a banked battery or a battery operated under slow-down conditions, are minimized, if not completely prevented.

In the accompanying drawings which, for purposes of exemplification, show preferred embodiments of coke oven batteries in which this invention can be practiced, to which batteries, however, the practice of the invention is not limited:

FIGURE 1 is a plot showing percent expansion (and contraction) of silica brick when subjected to different temperature conditions, i.e., is a graph showing the reversible thermal expansion of silica brick employed in the construction of the heating walls and regenerator division walls;

FIGURE 2 is a cross-wise vertical section through one type of uniflow coke oven battery; the left-hand half of this view passes through a coking chamber and the right-hand half through a fluid heating wall;

FIGURE 3 is a fragmentary longitudinal (in the direction of the length of the battery) vertical section through the battery of FIGURE 2',

FIGURE 4 is a cross-wise vertical section through the heating wall of one type of counterflow coke oven battery;

FIGURE 5 is a fragmentary longitudinal vertical section through the battery of FIGURE 4; and

FIGURE 6 is a fragmentary vertical section partly in elevation, on a greatly enlarged scale as compared with the scale of FIGURES 2 to 5, inclusive, showing a preferred form of gas inlet construction to a regenerator, in which construction flow of gas is controlled by the reversing mechanism which controls the flow of heating gas to the inflow flues.

Referring first to FIGURE 1, it will be noted that at temperature increases or decreases above 1200 F., signilicant expansion (or contraction on temperature decrease to a value above 1200" F.) of silica brick of which the heating walls and regenerator division walls are composed, does not take place. Temperature changes within the range of 1200 to 1000 F. causes contraction or expansion of the silica brick, as the case may be, of about .8%, within the range of from 1000" to 800 F. contraction or expansion, as the case may be, of the silica brick of the same magnitude takes place, and within the range of from 800 to 600 F. the contraction or expansion of the silica brick, as the case may be, is of the order of 1.2%. In normal coke oven operation coking a charge of coal in each coking chamber at the usual rate of from say 16 to 18 hours, the temperatures in the end flues is usually about 2200 F. Operated as heretofore conventional in a banked state or under slow-down conditions by burning coke oven gas or natural gas in the flues at a reduced rate, the temperature in the end flues is usually about i700 to 1750 F. This temperature change does not give rise to excessive contraction stresses (or expansion stresses upon resumption of normal operation) in the heating walls. However, under such conditions of operation in the banked state or under slow-down conditions with an end flue temperature of about 1700 to 1750" F., the temperature of the silica brick at the base of the regenerators, drop from a normal minimum temperature of about 65 to 750 F. to a minimum temperature at this point of about 300 to 400 F. The temperatures in the remainder of the regenerators and in the regenerator superstructure are corerspondingly reduced. Such temperature drop, as noted above, causes a contraction of the order of 5 or 6 inches in the length of a regenerator wall about 40 feet long and even more in the longer walls of modern coke oven batteries.

FIGURES 2 and 3 show a uniflow coke oven battery comprising coking chambers 10 flanked by heating walls 11, each of which has the flues arranged in two groups, i.e., the coke oven battery shown is of the two-divided type. The flues in each heating wall of one group are all identified by the reference character 12 and those of the other group by the reference character 13. Flow takes place up through one group of flues, say 12, through the connecting duct 14 and down through the other group 13; upon reversal, flow takes place up through group 13, through duct 14 and down through 12. Each heating flue has at its base a gas gun or burner 15. The gas guns or burners 15 of each group 12 of each heating wall communicates with a gas supply line 16 connected by conduit I7 with gas main 18 on the left-hand side of the battery viewing FIGURE 2. The gas guns or burners 15 of each group 13 of each heating wall communicate with a gas supply line 16 connected by conduit 17' with gas main 18 on the right-hand side of the battery.

Each coking chamber 10, as conventional, is provided at its top with any desired number of charging holes and uptake pipes 19 leading into collector mains 26. The opposite ends of the coking chambers are designed to be closed with the usual self-sealing doors 2 1, one of which is shown in FIGURE 2.

The cross-wise extending regenerator dividing walls 22 are positioned directly beneath the heating walls as best shown in FIGURE 3. A dividing wall 24- disposed on the longitudinal median of the battery divides the regenerators into two groups of cross-wise extending regenerators. The regenerators of one of these groups are identified by the reference character 25 and are positioned on the left-hand side (viewing FIGURE 2) of dividing wall 24. The regenerators of the other group are each identified by the reference character 26 and are positioned on the right-hand side of dividing wall 24. All of the regenerators 25 operate for flow in the same direction, say

inflow, while all of the regenerators 26 operate for outflow; upon reversal, all of the regenerators 26 operate for inflow and all of the regenerators 25 for outflow.

Regenerators 26 each has at its base a duct 28 connected with chimney flue 29 through a passageway 31 flow-through which is controlled by a damper or valve 32. Regenerators 25 each has at its base a duct 33 connected with chimney flue 29 through a passageway flow-through which is controlled by a damper or valve, the same as valve 32. The dampers or valves 32 controlling flow through the respective passageways leading into chimney flue 29 control the admission of air to the inflow regenerators. They are operated by conventional reversing mechanism 34, so that the flow of air takes place through the ducts 33 into the regenerators communicating therewith; the valves controlling the flow of waste gases through ducts 28 are then open to permit the waste gas to exit from the then outflow regenerators into chimney flue 29. Upon reversal, valves 32. are positioned to close the communication between ducts 23 and the chimney flue 29, admit air to ducts 28 and place ducts 33 into communication with chimney flue 29.

The top of each regenerator is connected by ports 35, 36 with a pair of heating flues on opposite sides of each coking chamber directly above the regenerators, except for the end regenerators which are connected with the heating flues in the end heating walls. Each pair of ports 35, 36 lead into an inlet port 37 individual to each heating flue at the base thereof.

Each regenerator 25, 26, as conventional, is filled with refractory brick 43, e.g., clay, arranged for flow of the hot gases thereover during the outflow cycles, and for flow of air thereover during the inflow cycles in the case of the oven battery of FIGURES 2 and 3 which is designed to burn coke oven or natural gas in the fines supplied to the gas guns in the flues from the mains 13 and 18. The refractory material extends to the level 41 providing a space or plenum 42 at the top of each regenerator.

In the case of a combination oven, alternate regenerators of each row of side by side regenerators along the length of the battery are employed as an air inflow regenerator and the remaining regenerators of the row are employed as lean gas inflow regenerators, thus in eifect disposing the regenerators in each row in pairs, one member of each pair being an air inflow regenerator and the other a lean gas inflow regenerator. Air is supplied to one inflow regenerator of each pair and lean gas such as producer gas or blast furnace gas to the other inflow regenerator of each pair. The waste gases or products of combustion flow through both regenerators of each pair of regenerators n the opposite side of the battery, operating as outflow regenerators.

In accordance with this invention each regenerator has a fluid fuel inlet 43 desirably positioned in the end of the regenerator near the side wall of the battery in the space 42 just above the refractory brick 40. In the embodiment of the invention shown in FIGURES 2 and 3 the fluid fuel inlets 43 in the regenerators are connected by main 44 with the coke oven gas supply main 18 and those in the regenerators 26 are connected by main 44' with the coke oven gas supply main 18'. It will be appreciated that the fuel inlets 43 need not be supplied with coke oven gas but other suitable fluid fuels, pref erably high B.t.u. fuels such as natural gas or hydrocarbon oils may be introduced through the fuel inlets 43.

In the structure shown in FIGURE 6, the reversing mechanism 34' operated by the same mechanism which operates reversing mechanism 34 controlling the air flow to the regenerators and the waste gas outflow from the regenerators, operates a valve 45 controlling flow of gas from coke oven gas main 19 to the burners through line 46 and also a valve 52 controlling the flow of coke oven gas through line 44 to the fluid fuel inlet 43. There is, of course, one valve 45 and associated lines 44 and 46, the latter having a valve 52 therein, and fluid fuel inlet 43 for each regenerator 25 at the left-hand side of the battery, and for each regenerator 26 at the right-hand side of the battery. Thus, when the reversing mechanism is operated, actuation of valve 45 on the left-hand side of the battery during one cycle of operation interrupts the flow of coke oven gas to the flues 12, and supplies coke oven gas to the fluid fuel inlets 43, which coke oven gas is burned in the regenerators 25 then functioning as waste gas outflow regenerators. At the same time valves 45 on the right-hand side of the battery are positioned to supply coke oven gas from main 18' to the burners in the flues 13 and interrupt the supply of coke oven gas to the regenerators 26. Upon reversal, coke oven gas is supplied to regenerators 26 and not to the burners in the flues 13, and to the burners in the flues 12 and not to the regenerators 25.

The coke oven gas thus supplied to the outflow regenerators is burned therein. Oxygen required for the combustion of this gas is derived from that present in the waste hot gases or combustion products passing through the outflow regenerators. The amount of air supplied to the inflow flues to support combustion of the gas fed to these flues, whether coke oven gas, natural gas, or lean gas, is from 15% to 30% in excess of the stoichiometric amount required for combustion of the gas fed to the fines. This excess air is present in the combustion products leaving the outflow flues and flows through the regenerators and supports combustion of the fluid fuel supplied to the regenerators through the inlets 43.

Preferably a temperature responsive element 51, such as a thermocouple, is positioned at the base of each regenerator 25, 26 and controls the volume of gas supplied to fluid fuel inlet 43 to maintain the bases of the regenerators at a minimum temperature of say about 650 F. to 750 F. at the end of each outflow cycle. Element 51 in each regenerator controls an electrically operated valve 52 in line 44 associated with that regenerator to regulate the amount of gas supplied to fuel inlet 43 during the outflow cycle of the regenerator in which the inlet is disposed, to insure that the base of each regenerator and hence the entire regenerator is reheated by outflow of the combustion products from the flues augmented by those formed by burning the gas supplied to fuel inlet 43 to the desired level.

FIGURES 4 and 5 show a combination hairpin twinflue under jet oven embodying the present invention. In FIGURES 4- and 5 each heating wall 60, made of silica brick, comprise-s a series of twin flues 61, 62; 61 indicates the left-hand portion of each twin flue and 62 the righthand portion. Each flue 61 functions as an inflow flue while flue 62 functions as an outflow flue and vice versa. Beneath each heating wall 60 is a silica brick regenerator division wall 63 and parallel to and midway between each pair of walls 63 is a second silica brick division wall 64 forming between each pair of adjacent walls 63 a pair of cross-wise extending regenerators a, b. Along the length of the battery one pair of regenerators a, b are connected to all flues 61 on the opposite sides of the coking chamber 65 above. The flues 62 of each heating wall communicate with the next pair of cross-wise extending regenerators. Thus along the length of the battery a pair of cross-wise extending inflow regenerators for supplying air or air and lean gas to the inflow flues of each twin flue of a pair of heating walls alternate with a pair of cross-wise extending waste gas outflow regenerators for receiving the products of combustion from the outflow flues of each twin flue of a pair of contiguous heating walls. Since such construction of coke oven batteries is well known, it is believed further description thereof is unnecessary.

As conventional, the twin flue under jet oven shown is provided with one chimney flue on one side or with two chimney flues 66 (as shown) on opposite sides of the battery and air inlets 67 to be regenerators controlled by the valves or damper 68 operated by the reversing mechanism 68' of any well known type.

A rich gas main 69 is positioned at each side of the battery and each main is provided with a cross-wise extending line 71 for each heating wall from which extend the valve controlled upcomers 72 leading into the gas guns in the base of each flue. Each coking chamber 65 has in its top the usual charging holes and an uptake pipe 73 leading into a collector main 74.

In accordance with this invention fluid fuel inlets '75 are positioned on the top of each regenerator a, b at both ends. Fluid fuel, preferably coke oven gas if available, or natural gas is supplied to inlets 75 when the battery is operated in a banked state or under slow-down conditions during the flow of products of combustion from the outflow flues through the regenerators. Preferably, the volume of gas thus supplied to the outflow regenerators and which is burned (combustion is supported by the excess air fed to the flues in volume of 15% to 30% in excess of the stoichiometric amount required to support combustion of the gas fed to the flues) is controlled by the temperature at the base of each regenerator to insure the maintenance of the regenerators at a temperature above that at which excessive contraction of the regenerator division walls and superstructure does not take place.

It will be noted that the present invention minimizes, if not completely preventing, cracking and fissures from taking place in regenerative coke oven batteries during operation thereof in the banked state or under conditions of slow-down operation.

Since certain changes in carrying out the above process, which embodies the invention, may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. The improvement in the method of operating a regenerative coke oven battery during banked state or slowdown condition of operation, which battery has flued heating walls, the flues of which are connected to regenerators, and the flues and regenerators operate periodically for inflow of air through at least some of the regenerators to preheat the air and supply the preheated air to support combustion of gas fed to the inflow flues, the products of combustion passing through the outflow flues and thence through outflow regenerators, and upon reversal, said flues and regenerators operate for inflow of air through at least some of the regenerators which had previously operated for outflow to preheat the air and supply the preheated air to support combustion of gas fed to the flues previously operated for outflow and the products of combustion passing through the previously operated outflow flues and thence through the previously operated outflow regenerators, which improvement comprises introducing a fluid fuel into and burning said fuel in said outflow regenerators.

2. The improvement in the method of operating a regenerative coke oven battery during banked state or slow down condition of operation, which battery has flued heating walls, the flues of which are connected to regenerators, and the flues and regenerators operate periodically for inflow of air through at least some of the regenerators to preheat the air and supply the preheated air to support combustion of gas fed to the inflow flues, the products of combustion passing through the outflow flues and thence through outflow regenerators, and upon reversal, said flues and regenerators operate for inflow of air through at least some of the regenerators which had previously operated for outflow to preheat the an and supply the preheated air to support combustion of gas fed to the flues previously operated for outflow and the products of combustion passing through the previously operated outflow flues and thence through the previously operated outflow regenerators, which improvement comprises 8 burning a gas from the group consisting of coke oven gas and natural gas in the upper portion of each outflow regenerator and passing the resulting products of combustion together with the waste heat gases through said regenerator.

3. The improvement in the method of operating a regenerative coke oven battery during banked state or slowdown condition of operation, which battery has flued heating walls, the flues of which are connected to regenerators, and the flues and regenerators operate periodically for inflow of air through at least some of the regenerators to preheat the air and supply the preheated air to support combustion of gas fed to the inflow flues, the products of combustion passing through the outflow flues and thence through outflow regenerators, and upon reversal, said flues and regenerators operate for inflow of air through at least some of the regenerators which had previously operated for outflow to preheat the air and supply the preheated air to support combustion of gas fed to the flues previously operated for outflow and the products of combustion passing through the previously operated outflow flues and thence through the previously operated outflow regenerators, which improvement comprises burning a gas from the group consisting of coke oven gas and natural gas in the upper portion of each outflow regenerator and passing the resulting products of combustion together with the waste heat gases through said regenerator and controlling the amount of said gas burned in each outflow regenerator in accordance with the temperature at the lower portion of said regenerator to maintain the temperature therein at a level such that excessive contraction of the regenerator division walls does not take place.

4. The improvement in the method of operating a regenerative coke oven battery during a banked state or slow-down condition of operation, which battery has flued heating walls, the flues of which are connected to air inflow, lean gas inflow and waste gas outflow regenerators, and the flues and regenerators operate periodically for inflow of air and lean gas through the respective inflow air and inflow lean gas regenerators to the inflow flues where the air supports combustion of the lean gas fed to the inflow flues and the products of combustion flow from the outflow flues through the outflow regenerators and upon reversal air and lean gas is fed through the previously operated outflow regenerators into the previously operated outflow flues where combustion takes place and the products of combustion pass through the previously operated inflow flues and thence through the previously operated inflow regenerators, which improvements comprises introducing a fluid fuel into and burning said fuel in said outflow regenerators to maintain said regenerators at a temperature above that at which excessive contraction of the regenerator division walls takes place.

5. The method of operating a regenerative coke oven battery having flued heating walls constituted of inflow and outflow flues, flanking the coking chambers and inflow and outflow regenerators communicating, respectively, with the inflow and outflow flues, during banked state or slow-down condition of operation, which method comprises introducing gas in the inflow flues, introducing air from the air inflow regenerators into the inflow flues to support combustion of said gas, passing the products of combustion through the outflow flues and thence through the outflow regenerators, concurrently with the flow of said products of combustion through said outflow regenerators introducing and burning a fluid fuel in said outflow regenerators and periodically reversing the operation by introducing gas into the flues which had previously operated for outflow, introducing air to support combustion of said gas from regenerators which had previously operated for outflow and passing the resultant products of combustion through the flues which had previously operated for inflow and thence through the regenerators which had previously operated for inflow, and introducing a fluid fuel into and burning said fluid fuel in the regenerators while said regenerators operate for outflow.

6. The method of operating a coke oven battery as defined in claim 5 in which the regenerators comprise side by side air inflow, lean gas inflow and waste gas outflow 5 fined in claim 6 in which the volume of gas burned in the outflow regenerators is controlled in accordance with the temperature of the gases existing from the outflow regenerators.

References Cited in the file of this patent UNITED STATES PATENTS 492,400 Hofirnann Feb. 28, 1893 2,067,864 Sterling Jan. 12, 1937 10 2,396,461 Dougherty et al Mar. 12, 1946 2,978,386 M'acDonnell et al Apr. 4, 1961 CERTIFICATE OF CORRECTION Patent No 3 l33,869

May 19, 1964 Frans Wethly the above numbered patcertified that error appears in s Patentshould read as It is hereby on and that the said Letter ent requiring correcti corrected below Column 5, line 71 for "19 read 18 column 6 line 75 for "be" read the column 8 line 49 Q for "improvements" read improvement column 10, line 3 for "existing" read exiting Signed and sealed this 22nd day of September 1964a (SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Commissioner of Patents Aitesting Officer 

3. THE IMPROVEMENT IN THEMETHOD OF OPERATING A REGENERATIVE COKE OVEN BATTERY DURING BANKED STATE OR SLOWDOWN CONDITION OF OPERATION, WHICH BATTERY HAS FLUED HEATING WALLS, THE FLUES OF WHICH ARE CONNECTED TO REGENERATORS, AND TEH FLUES AND REGENERATORS OPERATE PERIODICALLY FOR INFLOW OF AIR THROUGH AT LEAST SOME OF THE REGENERATORS TO PREHEAT THE AIR AND SUPPLY THE PREHEATED AIR TO SUPPORT COMBUSTION OF GAS FED TO THE INFLOW FLUES, THE PRODUCTS OF COMBUSTION PASSING THROUGH THE OUTFLOW FLUES AND THENCE THROUGH OUTFLOW REGENERATORS, AND UPON REVERSAL, SAID FLUES AND REGENERATORS WHICH HAD PREVIOUSLY OPERATED FOR OUTFLOW TO PREHEAT THE AIR AND SUPPLY THE PREHEATED AIR TO SUPPORT COMBUSTION OF GAS FED TO THE FLUES PREVIOUSLY OPERATED FOR OUTFLOW AND THE PRODUCTS OF COMBUSTION PASSING THROUGH THE PREVIOUSLY OPERATED OUTFLOW FLUES AND THENCE THROUGH THE PREVIOUSLY OPERATED OUTFLOW RE- 